1. Field of the Invention
The present invention relates to the processing of electrical signals having complex waveforms such as, for example, signals provided by one or more sound responsive transducers. More specifically, this invention is directed to indicators and particularly to an improved meter device which provides an easily interpreted visual display of multiple characteristics of a received signal having a complex waveform. Accordingly, the general objects of the present invention are to provide novel and improved methods and apparatus of such character.
2. Description of the Prior Art
While not limited thereto in its utility, the present invention is particularly well suited for audio frequency signal monitoring or analysis and especially for use in the exercise of control over a recording process where both effective and peak amplitude are of interest. Since the amplitude of an audio waveform may vary faster than the needle of a moving movement meter can track and/or the human eye can follow, two common methods have evolved for quantifying amplitude information for such a complex waveform. The first of these two techniques is "peak reading" wherein an indication of the largest instantaneous amplitude excursion of the signal of interest is stored and displayed with the stored information being continuously updated. The second technique is to provide an indication of the RMS or effective value of the signal waveform. Simultaneous knowledge of both of these parameters is useful during the processing or use of the signal. The effective or RMS amplitude will provide an indication of the loundness or apparent volume of an audio derived input signal while knowledge of the peak amplitude provides useful information vis-a-vis the maximum signal handling capability of the processing equipment or the saturation characteristics of the medium, a magnetic tape for example, on which the signal is being stored.
There has not, in the prior art, been a single instrument having the capability of simultaneously providing an easily interperated display of both effective and peak amplitude of an input signal having a complex waveform.